Data commit

Task/Calkin-Wilf-sequence/Perl/calkin-wilf-sequence.pl

@@ -0,0 +1,33 @@
+use strict;
+use warnings;
+use feature qw(say state);
+
+use ntheory      'fromdigits';
+use List::Lazy   'lazy_list';
+use Math::AnyNum ':overload';
+
+my $calkin_wilf = lazy_list { state @cw = 1; push @cw, 1 / ( (2 * int $cw[0]) + 1 - $cw[0] ); shift @cw };
+
+sub r2cf {
+  my($num, $den) = @_;
+  my($n, @cf);
+  my $f = sub { return unless $den;
+               my $q = int($num/$den);
+               ($num, $den) = ($den, $num - $q*$den);
+               $q;
+             };
+  push @cf, $n while defined($n = $f->());
+  reverse @cf;
+}
+
+sub r2cw {
+    my($num, $den) = @_;
+    my $bits;
+    my @f = r2cf($num, $den);
+    $bits .= ($_%2 ? 0 : 1) x $f[$_] for 0..$#f;
+    fromdigits($bits, 2);
+}
+
+say 'First twenty terms of the Calkin-Wilf sequence:';
+printf "%s ", $calkin_wilf->next() for 1..20;
+say "\n\n83116/51639 is at index: " . r2cw(83116,51639);